here is link to the latest stable BIOS Framework Laptop 13 BIOS and Driver Releases (AMD Ryzen™ 7040 Series) and there is a description of “Battery Extender functionality”
there is beta BIOS if you are interested in Framework Laptop 13 Ryzen 7040 BIOS 3.17 Release BETA and driver pack Framework Laptop 13 AMD Ryzen™ 7040 Series Driver Bundle v2.07 2025_11_20 Release BETA